859343 Mercury FOAM

Table 1
Required Tools
Part Number Part Name Quantity
1U-5470
or
198-4240 Engine Pressure Group
or
Digital Pressure Indicator 1
238-5080 O-Ring Seal 1
5P-6944 Adapter 1
3J-1907 O-Ring Seal 1
6V-3965 Fitting 1
Illustration 1 g00294866
1U-5470 Engine Pressure Group
Check the fuel pressure of the engine with the 1U-5470 Engine Pressure Group. The engine pressure group includes Special Instruction, SEHS8907, "Using the 1U-5470 Engine Pressure Group". This instruction provides information about the usage of the group.Note: The fuel system pressure can also be checked using Caterpillar Electronic Technician Cat (ET). Refer to Troubleshooting, "Electronic Service Tools" for more information regarding ET.
Illustration 2 g02561516
198-4240 Digital Pressure Indicator Gp
Note: Refer to Special Publication NEHS0818, "Using the 198-4240 Digital Pressure Indicator Gp" for more information.
Illustration 3 g06431908
Left side view of the engine
(1) Plug
Illustration 4 g06431918
Right side view of engine
(2) Test port
Remove plug (1) from the secondary fuel filter base. Refer to Illustration 3.
Install the appropriate fittings into the fuel filter base, and connect the pressure gauge.
Start the engine and run the engine until the engine operating temperature is reached. At low rpm (700 to 900 rpm), the fuel pressure must be 650 50 kPa (94 7 psi). At high rpm (1800 to 2000 rpm), the fuel pressure must be 705 50 kPa (102 7 psi).Note: The typical fuel pressure of the engine at operating temperature can vary.The performance of the unit injector deteriorates when the fuel pressure drops below 390 kPa (57 psi). low-power complaints and erratic operation can occur in this situation. Check for a plugged fuel filter or air in the fuel lines as possible causes for these complaints before replacing fuel system components.There are two available pressure regulator valves and there are two sets of pressures:
Equipped with 327-0376 Check Valve Gp. At cranking speed (100–135 rpm), The fuel pressure can be 500 kPa (72 psi). At low idle (700 to 900 rpm), the fuel pressure can be 500 to 700 kPa (72 to 101 psi). At high idle (1800 to 2000 rpm), the fuel pressure can be 600 to 900 kPa (87 to 131 psi).
Equipped with 228-7381 Check Valve Gp. At cranking speed (100–135 rpm), The fuel pressure can be 350 kPa (51 psi). At low idle (700 to 900 rpm), the fuel pressure can be 450 to 650 kPa (65 to 94 psi). At high idle (1800 to 2000 rpm), the fuel pressure can be 600 to 800 kPa (87 to 116 psi).Low Fuel Pressure
Low fuel pressure can cause low power. Low fuel pressure can also cause cavitation of the fuel which can damage the fuel injectors. The following conditions can cause low fuel pressure:
Plugged fuel filters
Debris in the check valves for the fuel priming pump
Debris in the fuel pressure regulator valve
Partially open check valve
Sticking or worn fuel pressure regulator valve in the fuel transfer pump
Worn gears in the fuel transfer pump
Debris in the fuel tank, fuel lines, or fuel system components that create restrictionsHigh Fuel Pressure
Excessive fuel pressure can cause fuel filter gaskets to rupture. The following conditions can cause high fuel pressure:
Plugged orifices in the fuel pressure regulator valve
Stuck fuel pressure regulator valve in the fuel transfer pump
Pinched fuel return line